Still can't reproduce it on the latest codebase. When I click on the icon, console logs 'TEST' once per click. Could it be that you handle this particular event somewhere else and log additional message there?

This may have been a problem with 4.2 Beta 1, but since then a big chunk of MVC code has been merged, so the situation has changed. Hey, that's what betas are for! :) Beta 2 should be available Real Soon Now.

As for tracing where it comes from, I'd suggest waiting for Beta 2 and trying this code with it. If it still fires twice, place debugger statement in the event handler and go up the stack to see where the event comes from. Chances are it's a similar chunk of code somewhere else in your application; you can try to differentiate by logging something else than just "TEST".